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Black Box Explains... Video extenders with built-in skew compensation.

To ensure the best video resolution, it’s important to match your video extension device with a compatible grade of cable. Some multimedia extenders are not designed to transmit video across... more/see it nowcable that’s higher than CAT5. In fact, with these extenders, the higher-grade cable may actually degrade video.

The problem is with the cable twists of CAT5e and CAT6 cables. To reduce signaling crosstalk, these higher-grade cables have tighter twists—and more of them—than CAT5 cable does. For this reason, the wire distance that an electrical signal has to travel is different for each pair. This doesn’t normally cause a problem with data, but if you’re sending higher-resolution analog video signals across long cables, you may see color separation caused by the video signals arriving at different times.

To avoid this, you could use only the lower-grade cable with the extenders. But what if you already have CAT5e or higher cable installed in your building, or you simply want the latest and greatest copper wiring? Order an extender receiver that features built-in skew compensation so it can work properly with higher cable grades at longer distances. collapse


Black Box Explains... RJ-48

An RJ-48 plug is often mistaken for RJ-45. On the outside, the two look identical—both are housed in a miniature 8-position jack. The difference is in the pairing of the... more/see it nowwires.

In RJ-48, two of the wires are for transmit, two are for receive, and two are for the drain. The last two wires are reserved for future use.

There are three subsets within RJ-48: RJ-48C, RJ-48X, and RJ-48S.

RJ-48C and RJ-48X are very similar. Both use lines 1, 2, 4, and 5 and connect T1 lines. The RJ-48C is more common. The difference is that RJ-48X connectors have shorting bars.

RJ-48S uses lines 1, 2, 7, and 8. It connects 56K DDS lines. collapse


Black Box Explains...Cable termination.


Carefully remove the jacketing from the cable and expose one inch of the insulated wire conductors. Do not remove any insulation from the conductors. When the... more/see it nowRJ-45 connector is crimped, the contacts inside will pierce the conductor insulation.


Untwist the wires to within 1/8" of the jacket. Arrange the wires according to the cable spec (568B in this case). Flatten and align the wires. Make one straight cut across all the conductors, removing approximately 1/2" to ensure the ends are of equal length.


Slide the wires into a connector. The cable jacket should extend into the connector about 1/4" for strain relief. Orient the wires so connector Pin 1 aligns with cable Pin 1, etc. Hold the connector in front of you. With the locking tab down, Pin 1 is on the far left.


Insert the connector into a crimp tool. Make sure you’re using the proper die. Firmly squeeze the handles. They’ll lock in a ratcheting action. A final click indicates the connector is firmly latched.


Check your work using a continuity tester or cable certifier rated for the cable standard you’re installing. Your tester should be able to check for shorts, opens, or miswires.


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Black Box Explains...FDDI

Fiber Distributed Data Interface (FDDI) is a networking standard for operating at speeds of up to 100 Mbps. The standard FDDI network is set up in a ring topology with... more/see it nowtwo rings that transmit signals in opposite directions to a series of nodes. FDDI accommodates up to 500 nodes per dual-ring network with spacing up to 2 kilometers between adjacent nodes. FDDI uses the same token-passing scheme as the IEEE 802.5 Token Ring network to control transmission around the loop. collapse


Black Box Explains... Bridges

If you work with legacy networks, you have doubtlessly encountered bridges. Bridges perform the same function as today’s switches in that they connect multiple network segments to create one homogenous... more/see it nownetwork, while keeping each segment isolated from the others.

Bridges operate on MAC-layer addresses and are protocol independent, so they transfer data between workstations without understanding the protocol. Since they don’t have to understand the protocol, they require little or no configuration.

Once you connect the bridge to the network, it automatically learns the addresses of all connected nodes and then creates an internal address table of this information.

When the bridge sees a packet, it checks the packet’s destination address against its internal list. If the address indicates the packet needs to be forwarded, the bridge passes the packet to the appropriate segment. If a bridge doesn’t know where a packet belongs—for example, when a station is first powered on—it passes on the packet.

Bridges can also distinguish between local data and remote data, so data traveling from one workstation to another in the same network doesn’t have to cross the bridge.

Although they are no longer in general use, Black Box stocks bridges for use as replacement parts in legacy networks. Replacing bridges with bridges rather than switches is often preferable because bridges are generally available with the BNC and AUI interfaces often found in older networks. Also, some bridges are able to link to other protocols such as RS-530 and X.21, enabling you to use these media to establish Ethernet network connections. collapse


Black Box Explains...Ethernet hubs vs. Ethernet switches.

Although hubs and switches look very similar and are connected to the network in much the same way, there is a significant difference in the way they function.

What is a... more/see it nowhub?
An Ethernet hub is the basic building block of a twisted-pair (10BASE-T or 100BASE-TX) Ethernet network. Hubs do little more than act as a physical connection. They link PCs and peripherals and enable them to communicate over a network. All data coming into the hub travels to all stations connected to the hub. Because a hub doesn’t use management or addressing, it simply divides the 10- or 100-Mbps bandwidth among users. If two stations are transferring high volumes of data between them, the network performance of all stations on that hub will suffer. Hubs are good choices for small- or home-office networks, particularly if bandwidth concerns are minimal.

What is a switch?
An Ethernet switch, on the other hand, provides a central connection in an Ethernet network in which each connected device has its own dedicated link with full bandwidth. Switches divide LAN data into smaller, easier-to-manage segments and send data only to the PCs it needs to reach. They allot a full 10 or 100 Mbps to each user with addressing and management features. As a result, every port on the switch represents a dedicated 10- or 100-Mbps pathway. Because users connected to a switch do not have to share bandwidth, a switch offers relief from the network congestion a shared hub can cause.

What to consider when selecting an Ethernet hub:
• Stackability. Select a stackable hub connected with a special cable so you can start with one hub and add others as you need more ports. The entire stack functions as one device.
• Manageability. Choose an SNMP-manageable hub if you have a large, managed network.

What to consider when selecting an Ethernet switch:
• Manageability. Ethernet switches intended for large managed networks feature built-in management, usually SNMP.
• OSI Layer operation. Most Ethernet switches operate at “Layer 2,” which is for the physical network addresses (MAC addresses). Layer 3 switches use network addresses, and incorporate routing functions to actively calculate the best way to send a packet to its destination. Very advanced Ethernet switches, often known as routing switches, operate on OSI Layer 4 and route network traffic according to the application.
• Modular construction. A modular switch enables you to populate a chassis with modules of different speeds and media types. Because you can easily change modules, the modular switch is an adaptable solution for large, growing networks.
• Stackability. Some Ethernet switches can be connected to form a stack of two or more switches that functions as a single network device. This enables you to start with fewer ports and add them as your network grows. collapse


Black Box Explains…OM3 and OM4.

There are different categories of graded-index multimode fiber optic cable. The ISO/IEC 11801 Ed 2.1:2009 standard specifies categories OM1, OM2, and OM3. The TIA/EIA recognizes OM1, OM2, OM3, and OM4.... more/see it nowThe TIA/EIA ratified OM4 in August 2009 (TIA/EIA 492-AAAD). The IEEE ratified OM4 (802.ba) in June 2010.

OM1 specifies 62.5-micron cable and OM2 specifies 50-micron cable. These are commonly used in premises applications supporting Ethernet rates of 10 Mbps to 1 Gbps. They are also typically used with LED transmitters. OM1 and OM2 cable are not suitable though for today's higher-speed networks.

OM3 and OM4 are both laser-optimized multimode fiber (LOMMF) and were developed to accommodate faster networks such as 10, 40, and 100 Gbps. Both are designed for use with 850-nm VCSELS (vertical-cavity surface-emitting lasers) and have aqua sheaths.

OM3 specifies an 850-nm laser-optimized 50-micron cable with a effective modal bandwidth (EMB) of 2000 MHz/km. It can support 10-Gbps link distances up to 300 meters. OM4 specifies a high-bandwidth 850-nm laser-optimized 50-micron cable an effective modal bandwidth of 4700 MHz/km. It can support 10-Gbps link distances of 550 meters. 100-Gbps distances are 100 meters and 150 meters, respectively. Both rival single-mode fiber in performance while being significantly less expensive to implement.

OM1 and 2 are made with a different process than OM3 and 4. Non-laser-optimized fiber cable is made with a small defect in the core, called an index depression. LED light sources are commonly used with these cables.

OM3 and 4 are manufactured without the center defect. As networks migrated to higher speeds, VCSELS became more commonly used rather than LEDs, which have a maximum modulation rate of 622 Mbps. Because of that, LEDs can’t be turned on and off fast enough to support higher-speed applications. VCSELS provided the speed, but unfortunately when used with older OM1 and 2 cables, required mode-conditioning launch cables. Thus manufacturers changed the production process to eliminate the center defect and enable OM3 and OM4 cables to be used directly with the VCSELS. OM3/OM4 Comparison
850 nm High Performance EMB (MHz/km)

OM3: 2000

OM4: 4700


850-nm Ethernet Distance
1-GbE
OM3: 1000 m

OM4: 1000 m


10-GbE
OM3: 300 m

OM4: 550 m


40-GbE
OM3: 100 m

OM4: 150 m


100-GbE
OM3: 100 m

OM4: 150 m

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Black Box Explains... Smart Serial Interface

Smart Serial is the Cisco router interface. It uses a space-saving 26-pin connector that automatically detects RS-232, RS-449, RS-530, X.21, and V.35 interfaces for both DTE and DCE devices based... more/see it nowon the type of cable used.

Smart Serial connectors can be found on Smart Serial cables and on the dual-serial-port WAN interface cards used in Cisco 2600 and 1720 series routers. The cables feature a Smart Serial connector on one end and a standard cable connector (such as DB25 or V.35) on the other end. The Smart Serial connector attaches to the dual-serial-port WAN interface card.

Each port on the WAN interface card features a Smart Serial connector. Ports can be configured independently to support two different physical interfaces. For example, you can run RS-232 cable to one port and RS-449 cable to the other port using a single WAN interface card.

What if you need to replace that RS-232 cable with V.35 cable? Just plug a Smart Serial–V.35 cable into the port. Because any Smart Serial connector on the WAN interface card attaches to any Smart Serial cable connector, no additional interface or adapter is necessary. Changing the configuration of your network is literally a snap! collapse


Black Box Explains...16850 UART.

The 16850 Universal Asynchronous Receiver/Transmitter (UART) features a 128-byte First In First Out (FIFO) buffer. When implemented with the appropriate onboard drivers and receivers, it enables your onboard serial ports... more/see it nowto achieve sustained data rates of up to 460.8 kbps.

The 16850 UART includes automatic handshaking (RTS/CTS) and automatic RS-485 line control. It also features external clocking for isochronous applications, a performance enhancement not offered by earlier UARTs. collapse


DisplayPort cable.

DisplayPort is a digital video interface that was designed by the Video Electronics Standards Association (VESA) in 2006 and has been produced since 2008. It’s incredibly versatile, with the capability... more/see it nowto deliver digital video, audio, bidirectional communications, and accessory power over a single connector.

DisplayPort cables are targeted at the computer world rather than at consumer electronics. DisplayPort is used to connect digital audio/video computers, displays, monitors, projectors, HDTVs, splitters, extenders, and other devices that support resolutions up to 4K and beyond. Unlike HDMI, however, DisplayPort is an open standard with no royalties.

With the proper adapters, DisplayPort cable can carry DVI and HDMI signals, although this doesn’t work the other way around—DVI and HDMI cable can’t carry DisplayPort. Because DisplayPort can provide power to attached devices, DisplayPort to HDMI or DVI adapters don’t need a separate power supply.

DisplayPort supports cable lengths of up to 15 meters with maximum resolutions at cable lengths up to 3 meters. Bidirectional signaling enables DisplayPort to both send and receive data from an attached device.

DisplayPort v1.1: 10.8 Gbps over a 2-meter cable.

DisplayPort v1.2: 21.6 Gbps (4K). DisplayPort v1.2 also enables you to daisychain up to four monitors with only a single output cable. It also offers the future promise of DisplayPort Hubs that would operate much like a USB hub.

DisplayPort v1.3: 2.4 Gbps. (5K)

The standard DisplayPort connector is very compact and features latches that don’t add to the connector’s size. Unlike HDMI, a DisplayPort connector is easily lockable with a pinch-down locking hood, so it can't be easily dislodged. However, a quick squeeze of the connector releases the latch.

The Mini DisplayPort (MiniDP or mDP) is a miniatured version of the DisplayPort interface. It carries both digital and analog computer video and audio signals. Apple® introduced the Mini DisplayPort connector in 2008 and it is now on all new Mac® computers. It is also being used in newer PC notebooks. This small form factor connector fully supports the VESA DisplayPort protocol. It is particularly useful on systems where space is at a premium, such as laptops, or to support multiple connectors on reduced height add-in cards.

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